An issue was discovered in PHPMailer before 5.2.22. PHPMailer's msgHTML method applies transformations to an HTML document to make it usable as an email message body. One of the transformations is to convert relative image URLs into attachments using a script-provided base directory. If no base directory is provided, it resolves to /, meaning that relative image URLs get treated as absolute local file paths and added as attachments. To form a remote vulnerability, the msgHTML method must be called, passed an unfiltered, user-supplied HTML document, and must not set a base directory.

Impact

Arbitrary local files can be attached to email messages.

Patches

Fixed in 5.2.22

Workarounds

Validate input before using user-supplied file paths.

References

https://nvd.nist.gov/vuln/detail/CVE-2017-5223

For more information

If you have any questions or comments about this advisory:

• Open a private issue in the PHPMailer project

References

• GHSA-4x5h-cr29-fhp6
• https://github.com/FriendsOfPHP/security-advisories/blob/master/phpmailer/phpmailer/CVE-2017-5223.yaml
• https://github.com/PHPMailer/PHPMailer/releases/tag/v5.2.22
• https://nvd.nist.gov/vuln/detail/CVE-2017-5223
• https://github.com/PHPMailer/PHPMailer/blob/master/SECURITY.md
• https://www.exploit-db.com/exploits/43056/
• http://kalilinux.co/2017/01/12/phpmailer-cve-2017-5223-local-information-disclosure-vulnerability-analysis/
• http://www.securityfocus.com/bid/95328